Chevrolet Trax: DTC B125C: Satellite antenna

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B125C 01

Satellite Antenna Circuit Short to Battery

DTC B125C 02

Satellite Antenna Circuit Short to Ground

DTC B125C 04

Satellite Antenna Circuit Open

Circuit/System Description

The digital radio receiver, located inside the radio, receives digital radio information from the digital radio antenna located on the outside of the vehicle. The digital radio receiver is connected to the digital radio antenna via a shielded coax cable. The digital radio antenna contains an amplifier which is powered by the radio through the coax cable.

Conditions for Running the DTC

This DTC is run every 300 milliseconds.

Conditions for Setting the DTC

The radio detects a circuit fault in the digital radio antenna.

Action Taken When the DTC Sets

The radio displays No XM Signal or Check Antenna.

Conditions for Clearing the DTC

• A current DTC clears when the condition for setting the DTC is no longer present.
• A history DTC clears after 100 malfunction-free ignition cycles.

Diagnostic Aids

The digital radio antenna requires a clear line of sight to the sky to operate properly. Reception may be limited, intermittent, or unavailable inside structures.

Reference Information

Schematic Reference

Radio/Navigation System Schematics (Encore), Radio/Navigation System Schematics (Trax)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT

CONNECTOR END VIEWS - INDEX - TRAX

Description and Operation

Radio/Audio System Description and Operation (with Monochrome Display), Radio/Audio System Description and Operation (with Color Display)

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Special Tools

EL-48028 Digital Radio Test Antenna

For equivalent regional tools, refer to Special Tools, Special Tools (MIT tool instructions).

Circuit/System Verification

1. With the vehicle outside in an area with an unobstructed view of the southern sky, tune to XM.
2. Verify DTC B125C is not set as current and the No XM Signal message is not displayed on the radio.

If DTC B125C is set as current or the No XM Signal message is displayed

Refer to Circuit/System Testing.

If DTC B125C is not set as current and the No XM Signal message is not displayed.

3. All OK.

Circuit/System Testing

1. Ignition OFF, disconnect the digital radio antenna coax cable from the A11 Radio. Connect the EL-48028 Digital Radio Test Antenna to the radio and place on the roof of the vehicle.
2. Ignition ON, radio tuned to XM channel 1.
3. Verify DTC B125C is not set as current and XM reception is improved.

If DTC B125C is set as current or XM reception is not improved

Replace the A11 Radio.

If DTC B125C is not set as current and XM reception is improved

4. Ignition OFF, disconnect the digital radio antenna coax cable from the T4G Cellular Phone, Navigation, and Digital Radio Antenna.
5. Verify the digital radio antenna coax cable passes the coax cable component test. Refer to Component Testing.

If the coax cable does not pass the test

Replace the antenna coax cable

If the coax cable passes the test

6. Test or replace the T4G Cellular Phone, Navigation, and Digital Radio Antenna.

Component Testing

CAUTION: Refer to Test Probe Caution .

NOTE: Before testing the coax cable, check the cable exterior for being pinched, cut, damaged, or having loose connections at the components, which can cause reception issues.

To prevent false reading when testing the center coax terminals, use care not to ground the test probe on the outer housing/shield.

Coax Cable Test

1. Ignition OFF, disconnect the coax cable at both components.
2. Test for less than 5 ohms between coax cable center terminal end to end.

If 5 ohms or greater

Replace the coax cable

If less than 5 ohms

3. Test for less than 5 ohms between the coax cable outer shield end to end.

If 5 ohms or greater

Replace the coax cable

If less than 5 ohms

4. Test for infinite resistance between the coax cable center terminal and the coax cable outer shield

If less than infinite resistance

Replace the coax cable

If infinite resistance

5. All OK

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Radio Antenna Base Replacement
• Control Module References for radio replacement, programming, and setup.

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